Physical and thermodynamic simulations of gamma-prime precipitation in Haynes® 282® using arc heat treatment

Cast nickel based superalloy, Grade Inconel 738, is a material for turbine blades. Its rejuvenation heat treatment usually consist of solution treatment condition with temperature range of 1125-1205 oC for 2-6 hours. Then it is following with double aging process including primary aging at 1055oC for 1 hour and secondary aging at 845oC for 24 hours. However, the various selected temperature dropping program were performed during solution treatment to simulate the possible error of heating furnace. The maximum number of temperature dropping during solution treatment is varied from 1-3 times From all obtained results, the various temperature dropping during solution treatment conditions showed extremely the significant effect on the final rejuvenated microstructures and long-term gamma prime stability after heating at temperature of 900oC for 200 hours.

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Finite Element Simulation and Optimisation of Ageing Precipitation in Nickel Base Superalloys with a Low Gamma-Prime (g’) Volume Fraction

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.172-174.881 ◽

2011 ◽

Vol 172-174 ◽

pp. 881-886 ◽

Cited By ~ 1

Author(s):

Franck Tancret ◽

Philippe Guillemet ◽

Florent Fournier Dit Chabert ◽

René Le Gall ◽

Jean François Castagné

Keyword(s):

Heat Treatment ◽

Finite Element ◽

Volume Fraction ◽

Nucleation And Growth ◽

Thermodynamic Quantities ◽

Gamma Prime ◽

The Matrix ◽

Element Approach ◽

Automatic Heat ◽

Nickel Base

A finite element approach is used to simulate the precipitation of Ni3(Al,Ti) intermetallics in nickel-based superalloys containing a low volume fraction of spherical g’ precipitates, in which precipitation occurs following nucleation and growth mechanisms. Classical differential equations of nucleation and growth are implemented in the software Comsol (formerly Femlab), to compute the number of precipitates per unit volume and their mean size. Another originality of the model is the use of thermodynamic quantities coming from phase diagram computations (Thermo-Calc), like the temperature variation of the equilibrium g’ volume fraction, and the evolution of the concentration of g’ forming elements (Al, Ti) in the matrix with the volume fraction of precipitates. Once adjusted to experiment in the case of isothermal ageings, the model can be used to simulate precipitation during complex thermal histories. Finally, automatic heat treatment optimisation procedures are proposed and tested, which can reduce heat treatment times by a factor of more than five.

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Taguchi Design for Heat Treatment of Rene 65 Components

10.31399/asm.cp.ht2019p0337 ◽

2019 ◽

Author(s):

Christina Maria Katsari ◽

Stephen Yue ◽

Andrew Wessman

Keyword(s):

Heat Treatment ◽

Volume Fraction ◽

Thermomechanical Processing ◽

Hold Time ◽

Turbine Blades ◽

High Strength ◽

Gamma Prime ◽

Nickel Based Superalloy ◽

Hold Temperature ◽

Microhardness Testing

Abstract Rene 65 is a nickel-based superalloy used in aerospace components such as turbine blades and disks. The microstructure in the as received condition of the superalloy consists of ~40% volume fraction of gamma prime precipitates, which gives such a high strength that thermomechanical processing is problematic. The goal of this study was to develop a heat treatment for manufacturing of Rene 65 components by changing the size distribution and volume fraction of those precipitates and lowering the strength. Gamma prime in this alloy is observed in three sizes, ranging from a few μm to tens of nm. For the design of the heat treatments, Design of Experiments (DOE) has been used; more specifically Taguchi’s L8 matrix. The four factors that are examined are cooling rate, hold temperature, hold time and cooling method to room temperature. The levels of the factors were two (high and low) with replication. Microstructures were characterized by Scanning Electron Microscopy and mechanical properties by Vickers microhardness testing.

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Combination of Microstructural Investigation and Simulation during the Heat Treatment of a Creep Resistant 11% Cr-Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.879.625 ◽

2016 ◽

Vol 879 ◽

pp. 625-630

Author(s):

Bernadette Gsellmann ◽

Dilek Halici ◽

Mihaela Albu ◽

Coline Beal ◽

Bernhard Sonderegger

Keyword(s):

Experimental Data ◽

Heat Treatment ◽

Grain Size ◽

Microstructural Evolution ◽

Point Of View ◽

Martensite Lath ◽

Microstructural Investigation ◽

Thermodynamic Simulations ◽

Lath Width ◽

Experimental Findings

This work deals with the microstructural evolution of creep resistant martensitic/ferritic 11% Cr-steel during thermomechanical treatment from an experimental as well as modeling point of view. The creep resistance of this material group is highly dependent on the precipitate status. The initial precipitate status is controlled by the chemical composition of the alloy and the heat treatment after casting or hot rolling. It is therefore of utmost interest to understand and model the precipitate kinetics during this process. Once the microstructural evolution has been modeled successfully, only minimum effort is required to computationally test variants in the composition or heat treatment in order to optimize the process. In this work, the material was hot rolled, austenitized and subsequently annealed. All heat treatments have been performed during dilatometry tests. In order to investigate the microstructural evolution during the process, specimens were extracted at definite stages of the treatment. The specimens were then investigated applying various microscopical techniques in order to quantify the microstructural features (grain size, martensite lath width and precipitate data). The experimental data were then compared to thermodynamic simulations (MatCalc). General data such as nucleation sites for precipitates were taken from literature, grain size and martensite lath widths from the experimental data. Simulations include equilibrium calculations and precipitate kinetic simulations. In general, the simulations showed good agreement with the experimental findings, with minor room for improvements. The work thus lays a solid ground for future improvements of the heat treatment process.

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The Effect of Post-heat Treatment on the Microstructures of Single Crystal DD6 Superalloy

High Temperature Materials and Processes ◽

10.1515/htmp-2015-0037 ◽

2016 ◽

Vol 35 (8) ◽

pp. 751-760

Author(s):

Dongfan Li ◽

Hangshan Gao ◽

Zhixun Wen ◽

Zhenwei Li ◽

Zhufeng Yue

Keyword(s):

Heat Treatment ◽

Single Crystal ◽

Volume Fraction ◽

Ageing Time ◽

Thermal Cycles ◽

Quenching Temperature ◽

Gamma Prime ◽

Precipitation Processes ◽

Temperature Transformation ◽

Equilibrium Volume Fraction

AbstractVarious thermal cycles at the end of solution heat treatment and their influences on microstructure of single crystal superalloy DD6 were studied by experiments. During various thermal cycles, the qualitative and quantitative microstructure of samples quenched of the transformations is microscopically characterized. This completely includes the large changes in volume fraction, size distribution and morphology of gamma prime precipitate experienced in the upper temperature transformation. Noticeable deviation from the equilibrium volume fraction of γ’ phase is detected in both the dissolution and precipitation processes above 1,120°C for both moderate cooling and heating rate; differences were mainly attributed to the unsteady nature of the turbulent flow. The growth and alignment of the γ’ precipitates are deeply influenced by several factors, e.g. ageing time, cooling rate and quenching temperature. In addition, interesting findings such as “labyrinth” and “cluster” morphologies were observed by scanning electron microscope. During precipitation processes, the complicated microstructure evolution is illustrated by considering the consecutive equilibrium shapes of a coherent precipitate, which grows under the interaction with its neighbors and the coherency of the precipitates improves their potential to resist dissolution.

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Effect of Two Different Solutionizing Heat Treatments on the Microstructure of the CMSX-4 Ni-Based Superalloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.246.15 ◽

2016 ◽

Vol 246 ◽

pp. 15-18

Author(s):

Agnieszka Szczotok

Keyword(s):

Heat Treatment ◽

Heat Treatments ◽

Secondary Carbide ◽

Carbide Phases ◽

Gamma Prime ◽

Treatment Processes

The heat-treatment processes for the precipitation-strengthened nickel-based superalloys are extremely complicated. The solution heat treatments are designed to dissolve the gamma-prime and the secondary carbide phases and allow the optimum re-precipitation of these phases upon cooling or after aging, for various precipitation-strengthened superalloys. The study was conducted to examine the effects of two solutionizing heat treatments on the microstructure of the CMSX4 superalloy. A comparison between the two obtained microstructures was performed.

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Designing Experiments to Affect Post Weld Heat Treatment Parameters: Using the Full Factorial Design in Inconel X-750 Welds

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.711.188 ◽

2013 ◽

Vol 711 ◽

pp. 188-194

Author(s):

Prachya Peasura ◽

Bovornchok Poopat

Keyword(s):

Heat Treatment ◽

Factorial Design ◽

High Hardness ◽

Post Weld Heat Treatment ◽

Solution Temperature ◽

P Value ◽

Gamma Prime ◽

Time Interaction ◽

Hardness Increase ◽

Weld Heat

Alloy X-750 also has excellent properties down to cryogenic temperatures high stability and strength at high temperatures. This reason the alloy is used in manufacturing of gas turbine hot components. The research was study the effect of post weld heat treatment (PWHT) parameter on hardness and microstructure. The specimen was Inconel X-750 grade sheet of 2.8 mm thickness. This 23factorial design was used in experimental various post weld heat treatment at 705 and 845°C for 20 and 24 hour including solution temperature at 1,000 and 1,150°C. The welded specimens were tested by hardness testing in fusion zone (FZ) and heat affected zone (HAZ). The result showed that both of solution temperature, PWHT temperature and PWHT time interaction on hardness of FZ and HAZ at 95% confidential (P value < 0.05). The PWHT temperature and PWHT time interaction effect was the largest. The factor showed in the hardness increase with the low level (-1) of PWHT temperature and PWHT time for the hardness while it trended decrease for the solution temperature. The microstructure was the γ amount and small size would result in high hardness. Experimental results showed that the solution temperature at 1,150°C, PWHT temperature 705°C PWHT time of 20 hours provided intensity of gamma prime (γ) and MC carbide resulting in higher hardness both in FZ and HAZ.

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High Temperature Tensile Behavior of Directionally Solidified MAR-M247 Superalloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.783-786.1153 ◽

2014 ◽

Vol 783-786 ◽

pp. 1153-1158

Author(s):

Hui Yun Bor ◽

Chao Nan Wei ◽

An Chou Yeh ◽

Wei Bin He ◽

Huei Sen Wang ◽

...

Keyword(s):

Heat Treatment ◽

High Temperature ◽

Room Temperature ◽

Solution Treatment ◽

Standard Heat Treatment ◽

Directionally Solidified ◽

Gamma Prime ◽

Elongation To Failure ◽

Initial Fracture ◽

High Temperature Tensile

In this study, two heat treatment schemes were proposed to study the high temperature mechanical behavior of directionally solidified MAR-M247 superalloy. Two withdraw rates, namely, 60 and 180 mm/h were used to produce directionally solidified MAR-M247 specimens by the Bridgeman type furnace. Standard heat treatment (HT1) procedures are solution treatment at 1230°C for 2 h/ArC, then first aging at 980°C for 5 h/AC and followed by second aging at 870°C for 20 h/AC. Modified heat treatment (HT2) is solution treatment at 1260°C for 3 h/ArC and first aging at 980°C for 6 h/AC, then the same second aging procedure. Uneven size, shape and fusion-alike of gamma prime precipitates are observed after full HT1 scheme, whereas even size but fine gamma prime precipitates are observed in HT2 specimen. All three tensile properties (elongation to failure, ultimate tensile strength and yield strength) of HT2 specimens are higher than these of HT1 specimens either at room temperature 25°C or at high temperature 982°C for both withdraw rates. Uneven distribution of the γ′ precipitates attributes to the initial fracture of HT1 specimens.

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